1. Field of the Invention
The present invention relates to a wire clamper for a bonding apparatus for clamping a wire upon cutting the wire at a bonding point after completion of a wire bonding process during fabrication of a semiconductor device.
2. Description of the Prior Art
A wire bonding process is carried out as shown in FIG. 10 during fabrication of a semiconductor device. Specifically, a wire 51 in the form of a fine line of metal, such as gold or aluminum, is drawn out from a spool 50 and extended to a capillary tool 54 via a guide 52 and a wire clamper 53. The wire 51 is inserted into the capillary tool 54 and drawn out from a lower end of the capillary tool 54 by a given length. In this state, a ball is formed at a lower end of the drawn-out wire 51 using a torch or the like. Then, the capillary tool 54 is moved to a position just above an electrode 57 of a semiconductor component 56 fixed on an island 55 of a lead frame, and then lowered so that the ball is pressed onto the electrode 57 and bonded thereto. Subsequently, the capillary tool 54 is moved to a position just above a bonding point 59 of an external lead terminal 58 and then lowered so that the wire 51 drawn out from its lower end is pressed onto the bonding point 59 so as to be bonded thereto. Then, the capillary tool 54 is raised along with the wire clamper 53 which is fixed to the capillary tool 54. When the capillary tool 54 is moved upward by a distance corresponding to the foregoing given length, the wire clamper 53 clamps the wire 51 between a pair of clamping pieces 53a, 53b thereof. As a result, the wire 51 is cut just above the bonding point 59 so that the wire bonding for that portion is finished.
In the prior art, the wire clamper 53 may be of a type where the clamping pieces 53a, 53b are driven by a push-pull solenoid, of a type where they are driven by a voice coil linear motor or of a type where they are driven by a piezo-electric element.
However, the clamper of the push-pull solenoid type has disadvantages that the response speed is low and thus there is a limit to the speed-up of the bonding operation, that a fine adjustment of the clamping pressure is difficult and that the structure of the clamper becomes complicated. The clamper of the voice coil linear motor type has disadvantages that the structure of the clamper becomes complicated similar to the push-pull solenoid type and is increased in size. The clamper of the piezo-electric element type has disadvantages that, although the size reduction is achievable, the production cost is high since materials of the element are formed into a laminated structure, and that the high voltage is required for driving the clamper, resulting in high breakage rate and short life and further resulting in complicated power circuit.